feat(security): unify workspace_root boundary enforcement across CLI and gateway

Promote workspace_root from channel-specific (magicform) to agents.defaults
so both CLI --workspace/--config-dir and gateway metadata overrides are
validated against the same immutable boundary. Paths must be relative
subdirectories — absolute paths, .., and empty/dot are rejected. The
boundary is snapshotted before overlay merges and cannot be widened by
workspace config files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cmd/picoclaw/internal/agent/helpers.go

@@ -16,6 +16,7 @@ import (
 	"github.com/sipeed/picoclaw/pkg/bus"
 	"github.com/sipeed/picoclaw/pkg/config"
 	"github.com/sipeed/picoclaw/pkg/logger"
+	"github.com/sipeed/picoclaw/pkg/pathutil"
 	"github.com/sipeed/picoclaw/pkg/providers"
 )
 
@@ -38,13 +39,27 @@ func agentCmd(message, sessionKey, model string, debug bool,
 		return fmt.Errorf("error loading config: %w", err)
 	}
 
-	// Apply workspace-local config overrides from config-dir
+	// Snapshot workspace_root from the base config before any overlay can touch it.
+	workspaceRoot := cfg.Agents.Defaults.WorkspaceRoot
+
+	// Validate and resolve --workspace and --config-dir against workspace_root.
+	var resolveErr error
+	workspace, configDir, resolveErr = validateWorkspacePaths(workspaceRoot, workspace, configDir)
+	if resolveErr != nil {
+		return resolveErr
+	}
+
+	// Apply workspace-local config overrides from config-dir.
+	// mergeAgentDefaults will re-validate any workspace field from the overlay
+	// against the snapshotted workspace_root.
 	if configDir != "" {
 		wc, wcErr := config.LoadWorkspaceConfig(configDir)
 		if wcErr != nil {
 			return fmt.Errorf("error loading workspace config from %s: %w", configDir, wcErr)
 		}
-		cfg.MergeWorkspaceConfig(wc)
+		if mergeErr := cfg.MergeWorkspaceConfig(wc); mergeErr != nil {
+			return fmt.Errorf("error merging workspace config from %s: %w", configDir, mergeErr)
+		}
 	}
 
 	// CLI flags win over workspace config
@@ -52,7 +67,7 @@ func agentCmd(message, sessionKey, model string, debug bool,
 		cfg.Agents.Defaults.ModelName = model
 	}
 
-	// Workspace override
+	// Workspace override (already validated above)
 	if workspace != "" {
 		cfg.Agents.Defaults.Workspace = workspace
 		os.MkdirAll(workspace, 0o755)
@@ -162,6 +177,27 @@ func applySkillsFilter(cfg *config.Config, skills []string) {
 	}
 }
 
+// validateWorkspacePaths resolves --workspace and --config-dir against workspace_root.
+// Both must be relative subdirectories of workspace_root. Returns the resolved
+// absolute paths or an error if validation fails.
+func validateWorkspacePaths(workspaceRoot, workspace, configDir string) (string, string, error) {
+	if workspace != "" {
+		resolved, err := pathutil.ResolveWorkspacePath(workspaceRoot, workspace)
+		if err != nil {
+			return "", "", fmt.Errorf("invalid --workspace: %w", err)
+		}
+		workspace = resolved
+	}
+	if configDir != "" {
+		resolved, err := pathutil.ResolveWorkspacePath(workspaceRoot, configDir)
+		if err != nil {
+			return "", "", fmt.Errorf("invalid --config-dir: %w", err)
+		}
+		configDir = resolved
+	}
+	return workspace, configDir, nil
+}
+
 // copyBootstrapFiles copies recognized bootstrap files (AGENTS.md, IDENTITY.md,
 // SOUL.md, USER.md) from srcDir into the workspace directory.
 func copyBootstrapFiles(srcDir, workspace string) {

cmd/picoclaw/internal/agent/helpers_test.go

@@ -0,0 +1,140 @@
+package agent
+
+import (
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func mustAbs(t *testing.T, path string) string {
+	t.Helper()
+	abs, err := filepath.Abs(path)
+	require.NoError(t, err)
+	return abs
+}
+
+func TestValidateWorkspacePaths(t *testing.T) {
+	root := filepath.Join(t.TempDir(), "workspaces")
+
+	absRoot, err := filepath.Abs(root)
+	require.NoError(t, err)
+
+	tests := []struct {
+		name      string
+		root      string
+		workspace string
+		configDir string
+		wantWS    string // expected resolved workspace; empty if error expected
+		wantCD    string // expected resolved configDir; empty if error expected
+		wantErr   string // substring of expected error; empty means success
+	}{
+		{
+			name:      "valid workspace subdirectory",
+			root:      root,
+			workspace: "tenant1",
+			wantWS:    filepath.Join(absRoot, "tenant1"),
+		},
+		{
+			name:      "valid config-dir subdirectory",
+			root:      root,
+			configDir: "tenant1/config",
+			wantCD:    filepath.Join(absRoot, "tenant1", "config"),
+		},
+		{
+			name:      "both valid",
+			root:      root,
+			workspace: "tenant1",
+			configDir: "tenant1/config",
+			wantWS:    filepath.Join(absRoot, "tenant1"),
+			wantCD:    filepath.Join(absRoot, "tenant1", "config"),
+		},
+		{
+			name:      "empty flags are fine",
+			root:      root,
+			workspace: "",
+			configDir: "",
+		},
+
+		// --- workspace traversal ---
+		{
+			name:      "workspace traversal rejected",
+			root:      root,
+			workspace: "../escape",
+			wantErr:   "invalid --workspace",
+		},
+		{
+			name:      "workspace bare dotdot rejected",
+			root:      root,
+			workspace: "..",
+			wantErr:   "invalid --workspace",
+		},
+		{
+			name:      "workspace mid-path traversal rejected",
+			root:      root,
+			workspace: "a/../../../etc",
+			wantErr:   "invalid --workspace",
+		},
+
+		// --- config-dir traversal ---
+		{
+			name:      "config-dir traversal rejected",
+			root:      root,
+			configDir: "../escape",
+			wantErr:   "invalid --config-dir",
+		},
+		{
+			name:      "config-dir absolute path rejected",
+			root:      root,
+			configDir: "/etc/passwd",
+			wantErr:   "invalid --config-dir",
+		},
+
+		// --- no workspace_root configured (backward compat: falls back to filepath.Abs) ---
+		{
+			name:      "workspace without root uses Abs fallback",
+			root:      "",
+			workspace: "anything",
+			wantWS:    mustAbs(t, "anything"),
+		},
+		{
+			name:      "config-dir without root uses Abs fallback",
+			root:      "",
+			configDir: "anything",
+			wantCD:    mustAbs(t, "anything"),
+		},
+		{
+			name:      "workspace traversal without root still rejected",
+			root:      "",
+			workspace: "../escape",
+			wantErr:   "invalid --workspace",
+		},
+
+		// --- workspace resolves to root itself ---
+		{
+			name:      "workspace dot rejected",
+			root:      root,
+			workspace: ".",
+			wantErr:   "invalid --workspace",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ws, cd, err := validateWorkspacePaths(tt.root, tt.workspace, tt.configDir)
+
+			if tt.wantErr != "" {
+				require.Error(t, err)
+				assert.True(t, strings.Contains(err.Error(), tt.wantErr),
+					"error %q should contain %q", err.Error(), tt.wantErr)
+				return
+			}
+
+			require.NoError(t, err)
+			assert.Equal(t, tt.wantWS, ws)
+			assert.Equal(t, tt.wantCD, cd)
+		})
+	}
+}

config/config.example.json

@@ -1,6 +1,7 @@
 {
   "agents": {
     "defaults": {
+      "workspace_root": "/data/workspaces",
       "workspace": "~/.picoclaw/workspace",
       "restrict_to_workspace": true,
       "model_name": "gpt4",

pkg/agent/loop.go

@@ -21,6 +21,7 @@ import (
 	"unicode/utf8"
 
 	"github.com/sipeed/picoclaw/pkg/bus"
+	"github.com/sipeed/picoclaw/pkg/pathutil"
 	"github.com/sipeed/picoclaw/pkg/channels"
 	"github.com/sipeed/picoclaw/pkg/commands"
 	"github.com/sipeed/picoclaw/pkg/config"
@@ -637,6 +638,28 @@ func (al *AgentLoop) processMessage(ctx context.Context, msg bus.InboundMessage)
 	workspaceOverride := msg.Metadata["workspace_override"]
 	configDir := msg.Metadata["config_dir"]
 
+	// Defense-in-depth: validate workspace/configDir overrides against workspace_root
+	// even though the originating channel should have already validated them.
+	wsRoot := al.cfg.Agents.Defaults.WorkspaceRoot
+	if workspaceOverride != "" {
+		resolved, err := pathutil.ResolveWorkspacePath(wsRoot, workspaceOverride)
+		if err != nil {
+			logger.WarnCF("agent", "Rejecting workspace_override from metadata",
+				map[string]any{"workspace_override": workspaceOverride, "error": err.Error()})
+			return "", fmt.Errorf("invalid workspace_override in metadata: %w", err)
+		}
+		workspaceOverride = resolved
+	}
+	if configDir != "" {
+		resolved, err := pathutil.ResolveWorkspacePath(wsRoot, configDir)
+		if err != nil {
+			logger.WarnCF("agent", "Rejecting config_dir from metadata",
+				map[string]any{"config_dir": configDir, "error": err.Error()})
+			return "", fmt.Errorf("invalid config_dir in metadata: %w", err)
+		}
+		configDir = resolved
+	}
+
 	var allowedTools, allowedSkills []string
 	if v := msg.Metadata["allowed_tools"]; v != "" {
 		for _, t := range strings.Split(v, ",") {
@@ -812,7 +835,9 @@ func (al *AgentLoop) runAgentLoop(
 				map[string]any{"path": configSource, "error": err.Error()})
 		} else if wc != nil {
 			tmpCfg := al.cfg.Clone()
-			tmpCfg.MergeWorkspaceConfig(wc)
+			if err := tmpCfg.MergeWorkspaceConfig(wc); err != nil {
+				return "", fmt.Errorf("workspace config overlay rejected: %w", err)
+			}
 			if tmpCfg.Agents.Defaults.GetModelName() == "" {
 				tmpCfg.Agents.Defaults.ModelName = agent.Model
 			}

pkg/channels/magicform/init.go

@@ -8,6 +8,6 @@ import (
 
 func init() {
 	channels.RegisterFactory("magicform", func(cfg *config.Config, b *bus.MessageBus) (channels.Channel, error) {
-		return NewMagicFormChannel(cfg.Channels.MagicForm, b)
+		return NewMagicFormChannel(cfg.Channels.MagicForm, cfg.Agents.Defaults.WorkspaceRoot, b)
 	})
 }

pkg/channels/magicform/magicform.go

@@ -8,7 +8,6 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"path/filepath"
 	"strings"
 	"sync"
 	"time"
@@ -17,6 +16,7 @@ import (
 	"github.com/sipeed/picoclaw/pkg/channels"
 	"github.com/sipeed/picoclaw/pkg/config"
 	"github.com/sipeed/picoclaw/pkg/logger"
+	"github.com/sipeed/picoclaw/pkg/pathutil"
 )
 
 // WebhookPayload is the inbound payload from MagicForm.
@@ -55,6 +55,7 @@ type requestContext struct {
 type MagicFormChannel struct {
 	*channels.BaseChannel
 	config        config.MagicFormConfig
+	workspaceRoot string // effective root: channel-level fallback to global
 	httpClient    *http.Client
 	requests      sync.Map // chatID → *requestContext
 	ctx           context.Context
@@ -62,7 +63,11 @@ type MagicFormChannel struct {
 }
 
 // NewMagicFormChannel creates a new MagicForm channel.
-func NewMagicFormChannel(cfg config.MagicFormConfig, msgBus *bus.MessageBus) (*MagicFormChannel, error) {
+// globalWorkspaceRoot is the agents.defaults.workspace_root from the base config.
+// The channel uses its own config.WorkspaceRoot if set, otherwise falls back to
+// globalWorkspaceRoot. If neither is configured, the constructor returns an error
+// because workspace overrides cannot be validated without a root boundary.
+func NewMagicFormChannel(cfg config.MagicFormConfig, globalWorkspaceRoot string, msgBus *bus.MessageBus) (*MagicFormChannel, error) {
 	base := channels.NewBaseChannel(
 		"magicform",
 		cfg,
@@ -70,11 +75,21 @@ func NewMagicFormChannel(cfg config.MagicFormConfig, msgBus *bus.MessageBus) (*M
 		cfg.AllowFrom,
 	)
 
+	effectiveRoot := cfg.WorkspaceRoot
+	if effectiveRoot == "" {
+		effectiveRoot = globalWorkspaceRoot
+	}
+	if effectiveRoot == "" {
+		return nil, fmt.Errorf("magicform channel requires workspace_root to be configured " +
+			"(set channels.magicform.workspace_root or agents.defaults.workspace_root)")
+	}
+
 	ctx, cancel := context.WithCancel(context.Background())
 
 	ch := &MagicFormChannel{
 		BaseChannel:   base,
 		config:        cfg,
+		workspaceRoot: effectiveRoot,
 		httpClient: &http.Client{
 			Timeout: 30 * time.Second,
 		},
@@ -191,31 +206,11 @@ func (c *MagicFormChannel) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	go c.processWebhook(c.ctx, payload)
 }
 
-// resolveWorkspace validates and resolves the workspace path.
-// If workspace_root is configured, the workspace must be a relative path that
-// resolves under the root. If workspace_root is not configured, workspace is
-// rejected (no arbitrary path writes allowed).
+// resolveWorkspace validates and resolves the workspace path using the shared
+// pathutil.ResolveWorkspacePath boundary check. The effective workspace root is
+// determined at construction time (channel-level config with global fallback).
 func (c *MagicFormChannel) resolveWorkspace(workspace string) (string, error) {
-	root := c.config.WorkspaceRoot
-	if root == "" {
-		return "", fmt.Errorf("workspace_root not configured; workspace overrides are not allowed")
-	}
-
-	absRoot, err := filepath.Abs(root)
-	if err != nil {
-		return "", fmt.Errorf("invalid workspace_root: %w", err)
-	}
-
-	// Join the root with the provided workspace (which may be relative)
-	resolved := filepath.Join(absRoot, workspace)
-	resolved = filepath.Clean(resolved)
-
-	// Ensure the resolved path is under the root (prevents ../../../etc traversal)
-	if !strings.HasPrefix(resolved, absRoot+string(filepath.Separator)) && resolved != absRoot {
-		return "", fmt.Errorf("workspace path escapes workspace_root")
-	}
-
-	return resolved, nil
+	return pathutil.ResolveWorkspacePath(c.workspaceRoot, workspace)
 }
 
 // verifyToken checks the Authorization Bearer token using constant-time comparison.

pkg/config/config.go

@@ -10,6 +10,7 @@ import (
 	"github.com/caarlos0/env/v11"
 
 	"github.com/sipeed/picoclaw/pkg/fileutil"
+	"github.com/sipeed/picoclaw/pkg/pathutil"
 )
 
 // rrCounter is a global counter for round-robin load balancing across models.
@@ -181,6 +182,7 @@ type RoutingConfig struct {
 }
 
 type AgentDefaults struct {
+	WorkspaceRoot             string         `json:"workspace_root,omitempty"        env:"PICOCLAW_AGENTS_DEFAULTS_WORKSPACE_ROOT"`
 	Workspace                 string         `json:"workspace"                       env:"PICOCLAW_AGENTS_DEFAULTS_WORKSPACE"`
 	RestrictToWorkspace       bool           `json:"restrict_to_workspace"           env:"PICOCLAW_AGENTS_DEFAULTS_RESTRICT_TO_WORKSPACE"`
 	AllowReadOutsideWorkspace bool           `json:"allow_read_outside_workspace"    env:"PICOCLAW_AGENTS_DEFAULTS_ALLOW_READ_OUTSIDE_WORKSPACE"`
@@ -986,9 +988,10 @@ func (c *Config) Clone() *Config {
 
 // MergeWorkspaceConfig overlays allowed fields from a workspace config onto this config.
 // Fields NOT honored (infrastructure-level): Gateway, Heartbeat, Devices, Providers.
-func (c *Config) MergeWorkspaceConfig(wc *WorkspaceConfig) {
+// Returns an error if the overlay contains a workspace path that escapes workspace_root.
+func (c *Config) MergeWorkspaceConfig(wc *WorkspaceConfig) error {
 	if wc == nil || wc.Config == nil {
-		return
+		return nil
 	}
 	src := wc.Config
 
@@ -998,7 +1001,9 @@ func (c *Config) MergeWorkspaceConfig(wc *WorkspaceConfig) {
 	}
 
 	// agents.defaults: merge non-zero fields
-	mergeAgentDefaults(&c.Agents.Defaults, &src.Agents.Defaults)
+	if err := mergeAgentDefaults(&c.Agents.Defaults, &src.Agents.Defaults); err != nil {
+		return err
+	}
 
 	// agents.list: replace if workspace has entries
 	if len(src.Agents.List) > 0 {
@@ -1017,11 +1022,20 @@ func (c *Config) MergeWorkspaceConfig(wc *WorkspaceConfig) {
 
 	// session: merge non-zero fields (prevents cross-tenant identity leakage)
 	mergeSessionConfig(&c.Session, &src.Session)
+	return nil
 }
 
 // mergeAgentDefaults copies non-zero fields from src into dst.
-func mergeAgentDefaults(dst, src *AgentDefaults) {
+// WorkspaceRoot is intentionally NOT copied — it is a security boundary
+// set by the base config and must not be overridden by workspace overlays.
+// Returns an error if a workspace overlay attempts to escape the root boundary.
+func mergeAgentDefaults(dst, src *AgentDefaults) error {
 	if src.Workspace != "" {
+		if dst.WorkspaceRoot != "" {
+			if _, err := pathutil.ResolveWorkspacePath(dst.WorkspaceRoot, src.Workspace); err != nil {
+				return fmt.Errorf("workspace config overlay rejected: %w", err)
+			}
+		}
 		dst.Workspace = src.Workspace
 	}
 	if src.RestrictToWorkspace {
@@ -1066,6 +1080,7 @@ func mergeAgentDefaults(dst, src *AgentDefaults) {
 	if src.MaxMediaSize > 0 {
 		dst.MaxMediaSize = src.MaxMediaSize
 	}
+	return nil
 }
 
 // mergeSessionConfig copies non-zero fields from src into dst.

pkg/pathutil/resolve.go

@@ -0,0 +1,110 @@
+package pathutil
+
+import (
+	"fmt"
+	"path/filepath"
+	"strings"
+)
+
+// ResolveWorkspacePath resolves path against root and returns an absolute path
+// that is guaranteed to be a proper subdirectory of root.
+//
+// When root is set:
+//   - Empty string and bare "." are rejected (must pick a subdirectory).
+//   - Absolute paths are rejected (must use relative subdirectory names).
+//   - ".." traversal is rejected before any path joining occurs.
+//   - A valid relative path is joined to root and returned as an absolute path.
+//   - A post-join boundary check confirms the result stays within root.
+//
+// When root is empty, the function falls back to filepath.Abs(path) for
+// backward compatibility with callers that don't have a boundary configured.
+func ResolveWorkspacePath(root, path string) (string, error) {
+	if root == "" {
+		// No boundary configured — resolve raw path as absolute.
+		if path == "" {
+			return "", fmt.Errorf("workspace path is empty")
+		}
+		if containsTraversal(path) {
+			return "", fmt.Errorf("workspace path contains directory traversal")
+		}
+		return filepath.Abs(path)
+	}
+
+	// With a root boundary, path must be a non-empty relative subdirectory.
+	if path == "" {
+		return "", fmt.Errorf("workspace path must be a subdirectory of workspace_root, not root itself")
+	}
+
+	if isAbsoluteOrRooted(path) {
+		return "", fmt.Errorf("workspace path must be relative, got absolute path")
+	}
+
+	// Check traversal before Clean — Clean("foo/..") normalises to "." and
+	// would produce a misleading "not root itself" error instead.
+	if containsTraversal(path) {
+		return "", fmt.Errorf("workspace path contains directory traversal")
+	}
+
+	if filepath.Clean(path) == "." {
+		return "", fmt.Errorf("workspace path must be a subdirectory of workspace_root, not root itself")
+	}
+
+	absRoot, err := filepath.Abs(root)
+	if err != nil {
+		return "", fmt.Errorf("invalid workspace_root: %w", err)
+	}
+
+	resolved := filepath.Clean(filepath.Join(absRoot, path))
+
+	// Belt-and-suspenders: confirm the resolved path is a proper subdirectory
+	// of root even after Clean normalisation.
+	if !strings.HasPrefix(resolved, absRoot+string(filepath.Separator)) {
+		return "", fmt.Errorf("workspace path escapes workspace_root")
+	}
+
+	return resolved, nil
+}
+
+// containsTraversal detects ".." traversal in all four patterns:
+//
+//	bare ".."          — the path IS ".."
+//	starts with "../"  — e.g. ../etc
+//	ends with "/.."    — e.g. foo/..
+//	contains "/../"    — e.g. foo/../bar
+//
+// Both forward-slash and backslash variants are checked so that this
+// works correctly on Windows where either separator may appear.
+func containsTraversal(path string) bool {
+	if path == ".." {
+		return true
+	}
+
+	for _, sep := range []string{"/", `\`} {
+		if strings.HasPrefix(path, ".."+sep) {
+			return true
+		}
+		if strings.HasSuffix(path, sep+"..") {
+			return true
+		}
+		if strings.Contains(path, sep+".."+sep) {
+			return true
+		}
+	}
+
+	return false
+}
+
+// isAbsoluteOrRooted returns true if the path is absolute (e.g. C:\foo on
+// Windows, /foo on Unix) or rooted with a leading separator. On Windows,
+// filepath.IsAbs returns false for Unix-style "/foo" paths, but we still
+// reject them since they are not relative subdirectory names.
+func isAbsoluteOrRooted(path string) bool {
+	if filepath.IsAbs(path) {
+		return true
+	}
+	// Catch Unix-style rooted paths on Windows (e.g. "/etc/passwd").
+	if len(path) > 0 && (path[0] == '/' || path[0] == '\\') {
+		return true
+	}
+	return false
+}

pkg/pathutil/resolve_test.go

@@ -0,0 +1,227 @@
+package pathutil
+
+import (
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestResolveWorkspacePath_WithRoot(t *testing.T) {
+	root := filepath.Join(t.TempDir(), "workspaces")
+
+	tests := []struct {
+		name    string
+		path    string
+		wantErr string // substring of expected error; empty means success
+		wantRel string // expected relative suffix under root (checked on success)
+	}{
+		// --- valid paths ---
+		{
+			name:    "relative subdirectory",
+			path:    "tenant1",
+			wantRel: "tenant1",
+		},
+		{
+			name:    "nested subdirectory",
+			path:    "tenant1/project/sub",
+			wantRel: filepath.Join("tenant1", "project", "sub"),
+		},
+
+		// --- empty / dot ---
+		{
+			name:    "empty path rejected",
+			path:    "",
+			wantErr: "subdirectory of workspace_root",
+		},
+		{
+			name:    "dot path rejected",
+			path:    ".",
+			wantErr: "subdirectory of workspace_root",
+		},
+
+		// --- traversal: bare .. ---
+		{
+			name:    "bare dotdot rejected",
+			path:    "..",
+			wantErr: "traversal",
+		},
+
+		// --- traversal: starts with ../ ---
+		{
+			name:    "starts with dotdot slash",
+			path:    "../escape",
+			wantErr: "traversal",
+		},
+		{
+			name:    "starts with dotdot backslash",
+			path:    `..\\escape`,
+			wantErr: "traversal",
+		},
+
+		// --- traversal: ends with /.. ---
+		{
+			name:    "ends with slash dotdot",
+			path:    "foo/..",
+			wantErr: "traversal",
+		},
+		{
+			name:    "ends with backslash dotdot",
+			path:    `foo\..`,
+			wantErr: "traversal",
+		},
+
+		// --- traversal: contains /../ ---
+		{
+			name:    "contains slash dotdot slash",
+			path:    "a/../escape",
+			wantErr: "traversal",
+		},
+		{
+			name:    "contains backslash dotdot backslash",
+			path:    `a\..\escape`,
+			wantErr: "traversal",
+		},
+		{
+			name:    "deep traversal",
+			path:    "a/b/../../escape",
+			wantErr: "traversal",
+		},
+
+		// --- absolute paths ---
+		{
+			name:    "unix absolute path rejected",
+			path:    "/etc/passwd",
+			wantErr: "must be relative",
+		},
+	}
+
+	if runtime.GOOS == "windows" {
+		tests = append(tests, struct {
+			name    string
+			path    string
+			wantErr string
+			wantRel string
+		}{
+			name:    "windows absolute path rejected",
+			path:    `C:\Windows\System32`,
+			wantErr: "must be relative",
+		})
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := ResolveWorkspacePath(root, tt.path)
+
+			if tt.wantErr != "" {
+				if err == nil {
+					t.Fatalf("expected error containing %q, got nil (result: %s)", tt.wantErr, got)
+				}
+				if !strings.Contains(err.Error(), tt.wantErr) {
+					t.Fatalf("expected error containing %q, got: %v", tt.wantErr, err)
+				}
+				return
+			}
+
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			absRoot, absErr := filepath.Abs(root)
+			require.NoError(t, absErr)
+			want := filepath.Join(absRoot, tt.wantRel)
+			if got != want {
+				t.Fatalf("expected %q, got %q", want, got)
+			}
+		})
+	}
+}
+
+func TestResolveWorkspacePath_NoRoot(t *testing.T) {
+	tests := []struct {
+		name    string
+		path    string
+		wantErr string
+	}{
+		{
+			name: "relative path resolved via Abs",
+			path: "some/dir",
+		},
+		{
+			name:    "empty path rejected",
+			path:    "",
+			wantErr: "empty",
+		},
+		{
+			name:    "traversal rejected even without root",
+			path:    "../escape",
+			wantErr: "traversal",
+		},
+		{
+			name:    "bare dotdot rejected even without root",
+			path:    "..",
+			wantErr: "traversal",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := ResolveWorkspacePath("", tt.path)
+
+			if tt.wantErr != "" {
+				if err == nil {
+					t.Fatalf("expected error containing %q, got nil (result: %s)", tt.wantErr, got)
+				}
+				if !strings.Contains(err.Error(), tt.wantErr) {
+					t.Fatalf("expected error containing %q, got: %v", tt.wantErr, err)
+				}
+				return
+			}
+
+			if err != nil {
+				t.Fatalf("unexpected error: %v", err)
+			}
+
+			// Without root, should return filepath.Abs(path)
+			want, absErr := filepath.Abs(tt.path)
+			require.NoError(t, absErr)
+			if got != want {
+				t.Fatalf("expected %q, got %q", want, got)
+			}
+		})
+	}
+}
+
+func TestContainsTraversal(t *testing.T) {
+	tests := []struct {
+		path string
+		want bool
+	}{
+		// positive cases
+		{"..", true},
+		{"../foo", true},
+		{`..\\foo`, true},
+		{"foo/..", true},
+		{`foo\..`, true},
+		{"foo/../bar", true},
+		{`foo\..\bar`, true},
+		{"a/b/../../c", true},
+
+		// negative cases — dotdot as part of a name is fine
+		{"..hidden", false},
+		{"foo..bar", false},
+		{"tenant1", false},
+		{"a/b/c", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.path, func(t *testing.T) {
+			got := containsTraversal(tt.path)
+			if got != tt.want {
+				t.Fatalf("containsTraversal(%q) = %v, want %v", tt.path, got, tt.want)
+			}
+		})
+	}
+}